1. Field of the Invention
The present invention relates to a gear including a plurality of teeth to be engaged with teeth of a corresponding gear to thereby transmit a rotational motion between two shafts, and in particular, relates to a gear having a tooth profile that can reduce a stress generated on a tooth root side at the time of engagement with teeth of a corresponding gear and can increase a strength of teeth of the gear, and relates to a manufacturing method therefor.
2. Description of Related Art
Conventionally, numerous attempts have been made to increase a strength of teeth of a gear used in a power transmission mechanism, such as in an automobile, a precision machine, and the like.
This kind of gear includes a ring gear with teeth and tooth spaces, in which the teeth can be brought into engagement with a corresponding gear (pinion) via tooth flanks, in which the tooth flanks, after a final engagement point of the pinion, from a tooth top toward a tooth bottom, compared to standard tooth flanks, are made to approximate a trochoid, described by the pinion and projected into a normal section, the tooth spaces being embodied in cross section in the form of a pointed arch in the region of the tooth bottom (see, Published Japanese Translation of PCT Publication for Patent Application No. 2004-519644, for example).
However, in the gear disclosed in Published Japanese Translation of PCT Publication for Patent Application No. 2004-519644, since the tooth space between adjacent teeth is embodied when viewed in cross section in the form of the pointed arch in the region of the tooth bottom, a triangular-pointed recess hole is formed in the tooth bottom. In such a gear, a stress might tend to be concentrated to the recess hole of the tooth bottom during the engagement with the teeth of the corresponding gear, and accordingly, damage might be caused by the increased stress generated thereon. Thus, it is required to increase the strength of the entirety of the teeth, including the tooth bottoms.
Therefore, in view of the above problems, an object of the present invention is to provide a gear having a tooth profile that can reduce the stress generated on the tooth root side at the time of engagement with the teeth of the corresponding gear and can increase the strength of the teeth, and to provide a manufacturing method therefor.